Class-X SCIENCE Acids, Bases and Salts 1. During summer season, a milkman usually adds a very small amount of baking soda to milk. Why? 2. Tooth enamel is one of the hardest substances in our body. How does it undergo damage due to eating chocolates and sweets? How do toothpastes prevent this damage? 3. How are all the acids and bases similar? Explain. 4. Baking soda is used in small amounts in making breads and cakes. It helps to make thes4e soft and spongy. An aqueous solution of baking soda turns red litmus blue. It is also used in soda acid fire extinguisher. Use this information to answer the following questions i. How does baking soda help to make cakes and breads soft and spongy? ii. How does it help in extinguishing fire? iii. Is the pH value of baking soda solution lower than or higher than 7? 5. Dry HCl gas does not turn blue litmus red whereas hydrochloric acid does. Give one reason. 6. A student drooped few pieces of marble in dilute hydrochloric acid contained in a test tube. The evolved gas was passed through lime water. What change would be observed in lime water? Write balanced chemical equation when (i) gas was evolved (ii) gas was passed through lime water. 7. Answer the following questions i. Why is the formula of Plaster of Paris written as CaSO 4.½H2O? How is it possible to have half of water molecule attached to CaSO4? ii. Why is sodium bicarbonate an essential ingredient of most antacids? iii. Sodium bicarbonate is an essential ingredient of baking powder. What is the function of it? iv. When electricity is passed through aqueous solution of NaCl, three products are obtained. Why this process is called chlor-alkali process? 8. Fresh milk has a pH of 6. When it changes into curd, will its pH value increase or decrease? Why? 9. A compound which is prepared from gypsum has the property of hardening when mixed with a proper quantity of water. Identify the compound. Write the chemical equation for its preparation. For what purpose it is used in hospitals? 10. Why does tooth decay start when the pH of mouth is lower than 5.5? 11. What effect does an increase in concentration of hydrogen ion in a solution have on the pH of the solution? 12. Why does 1 M HCl solution have a higher concentration of H + ions than 1M CH3COOH solution? 13. Write the name and chemical formula of calcium compound used for disinfecting drinking water. How is this compound manufactured? 14. Why are acid not stored in metal containers? Containers made from which materials are safe to store acids? 15. How will you prepare bleaching powder? Give chemical reaction involved. Why is tartaric acid added along with sodium bicarbonate in baking powder? 16. What is pH? How does pH change on changing H+ concentration? How does acidic or basic nature change? Chapter – Magnetic Effect Of current 1. What is the basic difference between A.C and D.C. generator? 2. An electric fuse of rating 3A is connected in a circuit in which an electric iron of power 1 Kw is connected which operates at 220V. what would happen? Explain. 3. Overloading in an electric circuit causes fire. Common people are unaware of this fact. Ankit an intelligent student told people of his locality about overloading. What values are shown by ankit? 4. What are permanent magnets and electromagnets? Give two uses of each. 5. A student while studying the force experienced by a current carrying conductor in a magnetic field record following observations: (i) the force experienced by the conductor increases as the current is increased. (ii) the force experienced by conductor decreases as the strength of magnetic field is increased. Which of the two observations are correct and why? 6. State the rule to determine the direction of force experienced by a current carrying conductor in a magnetic field. How will this force get affected on (i) doubling the magnitude of current (ii) reversing the direction of flow of current. 7. What is the difference between alternating and direct current? How A.C can be converted in to D.C. 8. In a household circuit, which three colored wires are commonly used. What is the function of these wires? 9. Why it is prefer to connect the devices in parallel instead of series combination? 10. What would you suggest the people of your area regarding the safety measures in using electricity?